1. Field of the Invention
The present invention relates to a process for producing a semiconductor wafer by etching and, if appropriate, polishing of the semiconductor wafer.
2. The Prior Art
Processes for etching a semiconductor wafer are described, for example, in U.S. Pat. No. 5,451,267, EP 930 640 A2 and EP 673 545 B1. In these processes, an etching medium flows frontally onto an edge of the semiconductor wafer while the semiconductor wafer is rotating if appropriate. If a semiconductor wafer which has been treated in this manner is subsequently polished on one side, it is possible to detect an elevation in an edge region of the polished side of the semiconductor wafer, extending in annular form along the circumference of the semiconductor wafer. The surface structure of a semiconductor wafer of this prior art type is illustrated in FIG. 1.
It is an object of the present invention to provide a process for producing a semiconductor wafer in which the formation of the abovementioned elevation, which is known as an edge gutter, is avoided.
According to a first embodiment of the invention, this object is achieved by a process for producing a semiconductor wafer by etching the surface of the semiconductor wafer, with an etching medium flowing in a laminar flow along a direction of flow toward an edge of the semiconductor wafer. There is a protective shield placed in front of the edge and adjacent to the edge of the semiconductor wafer, so that the etching medium firstly flows onto the protective shield and not onto the edge of the semiconductor wafer. Then the etching medium is caused to have a laminar flow across the wafer surface.
According to a second embodiment of the invention, this object is achieved by a process for producing a semiconductor wafer by etching and polishing the semiconductor wafer. During the etching of the semiconductor wafer an etching medium is flowing in a laminar flow along a direction of flow toward an edge of the semiconductor wafer. The semiconductor wafer is inclined with respect to the direction of flow of the etching medium, so that there is an angle of less than 180xc2x0 between the direction of flow of the etching medium and a first side of the semiconductor wafer. Also there is an angle of greater than 180xc2x0 between the direction of flow of the etching medium and a second side of the semiconductor wafer, and the second side of the semiconductor wafer is subsequently polished after the etching step.